Natural killer (NK) cell sensitivity of phorbol ester-differentiated tumour cells correlates with disease activity in chronic B-lymphocytic leukaemia.

In a prospective study, 16 patients with chronic B-lymphocytic leukaemia (CLL) were repeatedly investigated for clinical and laboratory signs of disease activity during a period of 18 months. The leukaemic cells were induced to differentiate in vitro using a phorbol ester, TPA. Two differentiation-associated properties of the tumour cells, i.e. the amount of cytoplasmic immunoglobulin (C-IgM) and the increased sensitivity to lysis by natural killer (NK) cells, were expressed in parallel and both parameters were positively correlated with the clinical activity of leukaemia. Phorbol ester-induced phenotypic changes of the leukaemic cells may therefore be used for the in vitro monitoring of disease activity in CLL. The present markers may, in addition, be useful in molecular analysis of B cell differentiation.